This invention relates to a central injection device for internal combustion engines, and more particularly to such a device having a rotor with an impeller driven by the intake air stream, the rotor being mounted in a housing for rotation about a fixed fuel feed stud connected to a fuel feed conduit and extending into a central borehole of the rotor but without contacting the wall of the borehole. The device further has a fuel outlet opening lying within the rotor, the rotor having a lateral fuel outlet opening connected to a connecting passage leading within the rotor to the fuel outlet opening of the fuel feed stud, a narrow annulus being provided between the fuel feed stud and the wall of the rotor borehole. The discharge orifice of the annulus, as well as the lateral fuel outlet opening, is located above a fuel level established when the rotor is at rest in the rotor borehole. With such arrangement the rotor is sealed as any leakage fuel, which is displaced radially by centrifugal forces from the outlet opening of the fuel feed stud located between the fuel level, is picked up by the annulus.
A central injection apparatus of the aforedescribed type is generally disclosed in German Pat. No. 25 36 996 entitled "Carburetor for Internal Combustion Engines". In all operating phases of the internal combustion engine, carburetors, or rather, central injection devices, of the above type generally deliver a quantity of atomized fuel into the intake manifold which is in direct proportion to the quantity of air drawn in and which produce an air-fuel mixture which is properly adjusted to ensure quantities of toxic substances in the exhaust which lie below the allowable limits.
However, it has been shown in these central injection devices that the quantity of toxic substances in the exhaust can reach peak values during operation, exceeding the allowable limits. These peak values are essentially attributable to a completely uncontrolled delivery of leakage fuel from the narrow annulus between the fuel feed stud and the rotor into the intake manifold. Moreover, the quantity of fuel which is delivered by the rotor of the central injection apparatus of known construction and which bears a linear relationship with the quantity of air drawn in over the entire operating range of the internal combustion engine, is considered unsatisfactory for internal combustion engines which need an air-fuel mixture enriched with fuel at the full load range.